Iran and Saudi Arabia are two of the most important countries in the Middle East. Not only do they enjoy the most abundant natural resources, but also have a geopolitical situation that makes their international attitude significant in terms of the East-West political-economic discourse. These features call for an in-depth comprehension of the international as well as human rights approaches of these nation-States. Therefore, this article reviews the foundations of their legal systems, and their contributions to the development of international law and human rights. It concludes that despite few human rights drawbacks in Saudi, its overall contributions to the development of international organisations, peace and security in the region, and human rights law are far greater than those of Iran. But what are the causes of this outcome? To answer this question, establishing a link between national law and international attitude is at stake. This article analyses the constitutional legal foundations that make such a study more interesting.